Electric signaling system



1952 J. G. GORDON-WRIGHT 8 ELECTRIC SIGNALING SYSTEM Filed May 12, 1948Patented Jan. 29, 1 952 UNITED J STATES PATENT foFrI'cE' ELECTRICSIGNALING SYSTEM Application May12, 1948, Serial No. 26,597

In Great Britain June 14, 1947 2 Claims. (01. lit-s53) The presentinvention relates to electrical sigthe responding units are connectedbetween any nalling systems and :is more particularly conm one of thesephase leads and the neutral concerned with systems involving theapplication of ductoru In the drawing, connection to the live highfrequency-signals to electric supply mains lead is represented by theletter L and to the for the purpose of operating a number of re- 5neutral lead by the letter N and by way of exsponding devices connectedthereto at different ample two responding units RI and R2 for propoints.By, high frequency is meant high comducing the desired switchingoperations are pared with the frequency of the supply and in shownconnected between the neutral N and the practice a frequency withintheaudio ,rangeis phase leads LI and L2 respectively. These infoundmostappropriate. Systemsof this type clude relays ofthe oscillatingmagnet type somealready find considerable application for the contimesknown as galvanometer relays which are trol of street lighting and mayalso be used for mechanically tuned to the different cadences effectingtarifi change or some form of load and when energised at suitableintervals build up control. a swing suflicient to operate theircontacts.

Such systems have sometimes not provedper- 1 It is found that insuitable circumstances apfectly reliable because the applied signal hasplication of the signalling currents to one low been masked or mutilatedby surges or other tension network will result in the transmissionparasitics fromwhich electric supply systemsare of these currents overthehigh tension network never entirely free. These parasitics maybe dueto other low tension networks also. This method to switching operationsor possibly to signals of of injection thus avoids the specialinsulation similar type spilling over from adjacent netdifiicultieswhich arise if injection is made direct works. It is highly desirablethat in the event to the high tension network in order to be effecof anyfailure for this reason the operator should tive over a plurality of lowtension networks have some means of knowing that the transmisconnectedthereto. sion has not been effective so that suitable steps The manuallyoperable selector switches SAI may be taken to ensure that the requiredswitch and SAZ are coupled together so that they aling DB at O is infact performed, The chief ways occupy corresponding positions and theyobject of the invention is to provide improved are shown resting onunwired' contacts which arrangements for actually testing whetherthe maybe the normal position. The remaining signal has been properly appliedto the network 3 ,contacts of switch SAI extend to the contacts of andwhether the conditions then existing were galvanometer relays i thsignal th com such as to enable it to produce itsproper effect. trolerSRC for controlling'rhythms which may According to the invention, in anelectrical be injected into the alternating current supply signallingsystem employingaudio frequency cur- 1 network, while the remainingcontacts of switch rents SUDBIimDOSBd 0 e c c pp y ma s Or SA2 extend tocorresponding supervisory reeilecting switching operations ata-plurality 0f sponding devices such as SR which are conremote points,supervisory equipment associated nected to the network at thetransmitting point with thesignal transmitting equipment includes: andare similar to the responding devices which a unit similar to thoseemployed at thelremote 1 are to effect the required switchingoperations. points for responding to signals, the supervisory 40 If forexample the switch arms areset on conequipment; beingar-rangedto-control the signal tacts 3, the-rhythm relevant to a particular retransmitting equipment so asto cause the transmote controlling operationto be effected, say mission of a signal to be repeatedif itfails to theswitching on of street lights, is selected over produce satisfactoryoperation of the supervisory switch SAI, and the lead SLA whosecondition lim t. 7 i t is subsequently indicative of the operation orThe invention will be, better, understood from non-operation of thesupervisory relay SR in rethe following description ofone'methodoi?carrysponse to'the injected signal is selected over ing it into eiiect,reference being bad to the acswitch 8A2.

companying drawing; which shows by means of To initiate the transmissionof the signal seacircuit diagram. the application of the invenlected,the push button switch KTS is closed motion to a system using signals ofthe so-called mentarily, thereby operating relay A which locks cadencetype. By this is meant that the same up over itscontacts Al, atcontactsA2 operates signalling frequency is employed for a number ofrelay G and at contacts A3 and A4 closes points different signals andthe necessary distinction is in the paths to switches SAI and 8A2respecmade by applying the signals at different cadences 65 tively. e yG pO op r t n at C a G1 or rhythms towhich the responding devices areprepares a locking circuit forrelay F, at contacts mechanically tuned.-The arrangement contem- G2 energises, the motor starter of the voicefreplated is that the audio-frequency signalling curquency motoralternator VFMA. which proceeds rents are injected on to the phaseleadsLl, L2, to run up to speed, at contacts. G3 starts the L3 of a lowtension portion of the network and synchronous motor ST which is usedfor signal v.) timing purposes and at contacts G4 and G connects directcurrentpcsitive and n gative to the signal rhythm controller SEC. Thesynchronous motor ST drives cams which are arranged to actuate contactsSTI, STZ and ST3 which are operated cyclically. It will be assumBdtha-tone cycle of operations is executed in sixty seconds and, by way ofexample, contacts STI close six seconds after the start and remainclosed for the remainder of the cycle, contacts ST2 close twelve secondsafter STI and remain closed for eighteen seconds and contacts ST3 closefor two seconds six seconds before the end of the cycle. Thus the closedperiods are: STI, 6-430; 5T2, Ilia-36 and ST3, 5456.

The direct current connected up by relay G to e si nal rhythm contr leris pp d simultaneously to relay WG, the operation of which is slightlydelayed since it is of the slow-to-operate type, and. to the lower coilsof the galvanometer relays GA, GB and G0 in, series. When the coils of.t e relays are thus energised steadily, the magnets are. deflected so asto open contacts GAL G13 and-G0 contacts GB! and CI r ain effectual,however since it is assumed that the arm of switch SA! is s on ContactWhen relay WG operates, the lower galvanometer relay oils are disnneeted to p m t the magnets to swing in the reverse direction and theirrepective contacts then lose. Wh n t ts A los h upper coils o the relaysare ener is d momentarily nti the peration of lay XG and the oscilating. magnet of. re y GA i age-in fliected in suc d rection as to op nits contacts whe eupon relay re as s. It will be ap hat the mo ingsystem of relay G i p e to osc llate. at i s natural .fr u ncy a at laywi l operate and r lease in y hr i m- Contactors CA! and CA2 arenormally'closed o that the output of he ice equency o r alternator VFMAis normally short-circuited and is consequently not initiallytransmitted over leads Ll L2 and L3 to the supply network; However,eighteen seconds after the start of the signalling cycle contacts ST2closeto cause relay H to operate and, release in synchronism withcontacts whereupon the actuating coil CA associated with the contactorsis also alternately energised and de-energised to actuate the contactorsaccordingly. By this time the motor alternator has run up to speed sothat each time th contactors open, its output at an appropriatefrequency is extended over the resonant circuits including inductor IAand capacitor QA, inductor IB and capacitor QB and. inductor IC andcapacitor QC to leads L| L2 and L3 whence it is applied to the supplynetwork; In this manner regular pulses of voice frequency current areinjected into the network, as selected by the switch SAI, for theeighteen seconds during which contacts S'Ift remain closed.

It will be apparent that had the selector switch been set to a differentposition, the rhythm of the pulses would have been determined by thefrequency ofoscill'ation of the galvanometer relay associated with thatposition.

A already mentioned a number of supervisory responding; units such; asSR, eachof which conveniently embodies, two galvanometer relay elementsindividually tuned to respond to the pulses derived from twocorresponding transmitting galvanometer relays, are connected tolive andneutral conductors of the supply network at the t ansm tti g. P n

. If the cadence signal is; injected correctly into 4: the network andis not appreciably mutilated or masked, the appropriate galvanometerrelay of the supervisory responding unit SR will be set n operation andwill close its contacts. The voice frequency signal superposed on thesupply is applied to the resonant circuit comprising capacitor QD andinductor ID which is loosely coupled with a second resonant stagecomprising inductor IE and capacitor QE to provide a resonant band passfilter. The signal is rectified by the rectifier bridge RB and extendedto the local circuit containing the series. connected galvanometerrelays on and off. It will be assumed that relay on" is tuned to therhythm of the signal used for switching on street lights while relay oilis tuned to the rhythm for switching oil the street lights. Theoscillating magnets of both relays are deflected slightly due to theinitial D. C. pulse but only relay on will beat with the rhythm of thesignal and eventually after a plurality of pulses close its contacts onwhereupon the latching relay S is operated over its left-hand coil toclose contacts SI. These contacts then complete a circuit over lead SLAto relay B which operates and at contacts Bl prepares a circuit forrelay D, at contacts B2 opens a point in the circult for relay E and atcontacts B3 completes a locking circuit for itself and lights lamp LSRto indicate that the signal has beencorrectly re-.

ceived.

When the contacts ST3 subsequently close after 54 seconds, relay D'operates, lock up at contacts DI and at contacts D2 releases relay Awhich in turn releases relay G. The interaction of relays XG and GA isthen stopped and relay WG also releases. Relay D releases when contacts.ST3 open and when contacts STI open at the end Of the cycle the motorST comes to rest. The lamp indication may now be cancelled and relay Bre-.

leased by operating the push button KCSR, mo-

mentarily so that the circuit is fully restored to normal.

When it is required later to switch the street lights off, the selectorswitches SAI and SAZ are set on contacts 5 and the push button switchKTS is operated. The circuit functions in substanti'ally the same manneras beforev but in this case pulse signals appropriate to thegalvanometer relay GB are injected into the network and'the galvanometerrelay off embodied in the supervisory responding unit SR operates sothat the right-hand coil of the latching relay S is energised' andcontacts SI are restored to the position shown. A circuit is thencompleted over lead SLB and switch SA2 to operate relay B whichfunctions as before.

A further function of the circuit is to perform automatic remote controloperations at predetermined times under'control of a time switch. Thesignal's'appropriate to such operations are in- 2 jected and supervisedindependently of the selectorswitches but otherwise the'circuitfunctions as previously described. 7 V In this case the time switch TSassumed to be driven by a synchronous motor is set to close its 7contacts T5! at a predetermined time and when this occurs relay TAoperates, locks dependent upon relay D and performs the same functionsas relay A. However, whereas contacts A3 extend a positive batteryconnection to the coils of galvanometer relays GA, GB. and GC by way fselector switch SAI, contacts TAZ extend the connection direct to thoserelays. Similarly contacts, TA3' connect relay B direct to theappropriate switched live lead of the appropriate.

supervisory responding unit. It will be understood that the circuitscould readily be arranged to prevent the sending of signals by manualcontrol while the time switch control was effective or vice versa andthis might be desirable in practice.

Assuming now that switching on of the street lights is again required tobe effected but that during the injection mutilation of the signaloccurs to such an extent that the relay on a in the supervisoryresponding unit does not operate effectively. Consequently contacts SIare not changed over and relay B fails to operate. In this case whencontacts ST3 close, relay E operates over normal contacts B2 andthereupon at contacts El provides a locking circuit for itself, atcontacts E2 prevents the operation of relay D and at contacts E3operates relay C. Relay C looks at contacts Cl, at contacts C2 operatesrelay F, and at contacts C3 completes a circuit for the signal failurealarm bell AB. Relay F locks up at contacts Fl, at contacts F2 opens theinitial circuit for relay E and at contacts F3 prepares a circuit forrelay D. Relay E releases when contacts ST3 open. may be cancelled atany time by operating the push button switch KCA momentarily to releaserelay C.

Since relay D is not operated, relays A, G, F

and WG remain operated so that the motor ST continues to run and thesignal sequence is repeated as before when contacts STZ close. If thissecond injection is successful, as will generally be the case since itis improbable that muti- The audible alarm 3 lation or masking will beof so long a duration as to prevent it, relay B subsequently operates toindicate the correct response of the supervisory equipment as before.Relay B also operates relay D which results in the release of relays A,G,

WG and F. Finally relay D releases when contacts ST3 open. Theindication lamp LSR may be extinguished by operating switch KCSR, andthe circuit is then fully restored to normal.

If however the second injection also is unsuccessful, relay B againremains inoperative and lamp LSR again fails to light. When contacts ST3close, relay D operates over contacts E2 and F3 and brings down relaysA, G, WG and F assuming that relay C has already been released byoperation of key KCA. A circuit is then again completed for relay Ewhich in turn re-operates relay C so that the alarm is again sounded. Ifrelay C has not previously been released, it maintains relay F operatedso that re-energisation of relay E is not possible. Relay D releaseswhen contacts ST3 open and no further injection operation takes placesince relays A and G are deenergised. Clearly there would be nodifficulty in arranging for the injection operation to be repeated untilsuccessful if such an arrangement were found to serve any useful purposebut in practice it is likely that if two successive injections have beenunsuccessful some more serious trouble has developed which will requireinvestigation by the operator.

It may be mentioned that the arrangement shown whereby the coils of thegalvanometer relays in the equipment SRC are connected in series is aconvenient one in practice but the coils could also be connectedseparately to the contacts of the switch SAI, if necessary in serieswith suitable resistors. Moreover the provision of two coils for eachrelay is a convenient arrangement to ensure an adequate initial swingbut the effect could also be produced with a single coil.

The invention therefore provides a simple arrangement for improving theoperation of equipment for signalling over electric supply mains wherebygreater reliability and convenience are secured without any appreciableincrease in the amount of equipment required.

I claim:

1. An electrical signalling arrangement for operating a plurality ofswitching devices connected to electric supply mains at separated pointsand responsive respectively to signalling currents of audio frequency ofdifferent cadences superimposed on said mains comprising a source ofsignalling current located at a control station, means at said controlstation for applying said source to said supply mains at difierentcadences, a manually operable rotary selecting switch, a first Wiper onsaid switch arranged to select the particular cadence at whichsignalling current is applied, a plurality of switching devicesconnected to said supply mains at said control station and responsiverespectively to the different cadences at which signalling current maybe connected to said mains in accordance with circuits completed oversaid first wiper, contacts controlled by said switching devicesconnected to the bank contacts co-operating with a second wiper of saidswitch and means connected to said second wiper for terminating theapplication of said signalling current to said mains after apredetermined period if the switching device corresponding to thedesired cadence has been operated.

2. An electrical signalling arrangement for operating a plurality ofswitching devices connected to electric supply mains at separated pointsand responsive to periodic currents of audio frequency superimposed onsaid mains comprising a source 1 of signalling current located at acontrol station,

means at said control station for applying to said supply mains a signalof predetermined cadence,

a manually operable key and a time switch each arranged to render saidmeans effective, a manually operable rotary switch for selecting thecadence of said signal by circuits completed over a first wiper of saidswitch, a circuit controlled by said time switch independently of saidmanually operable switch for determining the cadence of said signal, aplurality of switching devices responsive respectively to signals ofdifierent predetermined cadences and individually connected to the bankcontacts associated with a second wiper of said switch, a furtherswitching device responsive to signals of the cadence determined by saidtime switch and means controlled by each of said switching devices forterminating the application of said signal after a predetermined period.

JOHN G. GORDON-WRIGHT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

